In recent years, there are many cases where a liquid crystal display device is used as a display device of a notebook computer monitor, a television receiver and the like. The liquid crystal display device includes a liquid crystal display panel, and a backlight unit that is disposed to oppose a rear surface of the liquid crystal display panel, wherein the liquid crystal display panel adjusts penetration ratio (penetration amount) of light from the backlight unit and displays an image on a front surface of the liquid crystal display panel.
The backlight unit is roughly classified into two kinds. One is a light guide plate type (edge-light type) that uses a light guide plate and inputs light from a side of the light guide plate, and the other is a direct type in which a light source is disposed to oppose a rear surface of a liquid crystal module. Request for thickness reduction and size reduction of the liquid crystal display device is increasing, and more and more liquid crystal display devices are employing the edge-light type that is a backlight unit thinner than the direct type backlight unit.
A conventional backlight unit is described with reference to drawings. FIG. 8 is an exploded perspective view of a conventional backlight unit that is used for a liquid crystal display device. A backlight unit 92 is a unit that outputs planar light to a rear surface of a liquid crystal display panel (not shown). As shown in FIG. 8, the backlight unit 92 includes: a backlight chassis 94; a plurality of LED lamps 96 that are light sources held by the backlight chassis 94; and a light guide plate 95 that is held by the backlight chassis 94 and outputs light from the LED lamp 96 as the planar light to the liquid crystal display panel. The light guide plate 95 is held by a side wall portion of the backlight chassis 94. Here, as shown in FIG. 8, the backlight unit 92 has a rectangular shape when viewed from front. And, the LED lamp 96 is disposed to output the light to both end surfaces of the light guide plate 95 in a long-edge direction (see JP-A-2001-14923 and JP-A-2001-34185).
However, there are many cases where a gap is formed between the backlight chassis 94 and the light guide plate 95. In these cases, it is impossible to position the light guide plate 95 with respect to the backlight chassis 94 with high accuracy, accordingly, the brightness of the light output from the backlight unit 92 declines and the light output position deviates.
There is a backlight unit that has a structure for positioning the backlight unit 94 and the light guide plate 95 with high accuracy. FIG. 9 is a front view of an improved version of the backlight unit that is shown in FIG. 8. As shown in FIG. 9, there is the backlight unit 92 in which the light guide plate 95 is provided with a plurality of cutouts 950; and a stud pin 97 disposed in the backlight chassis 94 and the cutout 950 are applied to each other to be positioned. As described above, by using the plurality of cutouts 950 and the stud pins 97 disposed corresponding to the cutouts 950, it is possible to correctly position the backlight chassis 94 and the light guide plate 95, accordingly, it is possible to output correct planar light to the liquid crystal display panel (not shown).